Video decoding device, method, and program

ABSTRACT

A video decoding device includes a demultiplexing unit which demultiplexes a video bitstream including video data of an encoded slice, first Supplemental-Enhancement-Information having information indicating segments where a refresh has completed in a current picture, and second Supplemental-Enhancement-Information having information indicating a synchronization starting picture and a synchronization completed picture, an extracting unit which extracts the information indicating segments where a refresh has completed in a current picture from a message which is part of the demultiplexed Supplemental-Enhancement-Information; and a video decoding unit which decodes image data from the demultiplexed video bitstream by using at least inter prediction, wherein the synchronization starting picture is a leading picture within a refreshing period, and the synchronization completed picture is the end position of the refreshing period.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 16/905,811 filed on Jun. 18, 2020, which is acontinuation application of U.S. patent application Ser. No. 16/457,157filed on Jun. 28, 2019, which issued as U.S. Pat. No. 10,728,579, whichis a continuation application of U.S. patent application Ser. No.14/409,220 filed on Dec. 18, 2014, which issued as U.S. Pat. No.10,511,862, which is a National Stage Entry of international applicationPCT/JP2013/003458, filed on May 31, 2013, which claims the benefit ofpriority from Japanese Patent Application 2012-141924 filed on Jun. 25,2012, the disclosures of all of which are incorporated in their entiretyby reference herein.

TECHNICAL FIELD

The present invention relates to a video coding technology, inparticular, a video coding technology using adaptive predictive coding,which performs compression by adaptively switching intra-picture codingand inter-picture predictive coding.

BACKGROUND ART

A video has a large amount of information, therefore it is necessary toperform compression encoding of the video with high efficiency when thevideo is recorded and transmitted as digital data. In order to realizehigh-efficiency compression, various elemental technologies are used forvideo compression encoding.

There is a predictive coding technology as one of the elementaltechnologies for video compression encoding. The predictive codingtechnology is a technology for, when respective pixels in a video aresequentially encoded, generating a predicted value of a pixel to becurrently encoded by using one or a plurality of temporally and/orspatially neighboring pixels and encoding a differential signal betweenan original signal and a predicted signal, instead of directly encodingthe original signal. Generally, since each of pixels in a video has ahigh correlation with temporally and/or spatially neighboring pixels,high-efficiency compression can be performed by using the predictivecoding technology.

One of predictive coding technologies is called intra-picture predictivecoding which performs prediction by referring a group of pixels includedin the same picture, and another technology is called inter-picturepredictive coding which performs prediction by referring a group ofpixels included in a different picture (referred to as a referencepicture). Generally, since there is a certain motion in a video, theinter-picture predictive coding technology is commonly used with amotion compensation technology for increasing prediction efficiency byusing spatial displacement information. Note that a “picture” representsa processing unit of a screen, corresponds to a field in a case where avideo image of the interlace format is encoded per field unit, while itcorresponds to a frame in a case where a video image of thenon-interlace format (the progressive format) is encoded and a videoimage of the interlace format is encoded per frame unit.

Generally, there is a higher correlation in a video, in particular,temporally than spatially. Therefore, the inter-picture predictivecoding technology of predictive coding technologies can achievehigh-efficiency compression in particular. On the other hand, there is acase when a temporal correlation is reduced remarkably in an entire orpartial screen on the basis of movement in a position relationshipbetween a foreground and a background or scene change by editing.Therefore, general video coding formats including ISO/IEC 14496-10advanced video coding (AVC) described in Non Patent Literature 1implement an adaptive predictive coding method for encoding partialimages as units obtained by subdividing a picture by adaptivelyswitching inter-picture predictive coding and intra-picture predictivecoding, or by adaptively switching one of inter-picture predictivecoding, intra-picture predictive coding, and intra-picture codingwithout prediction. A size of unit varies depending on video codingformats, but a rectangular area (referred to as a macroblock) including16 pixels in a vertical direction and 16 pixels in a horizontaldirection is typically used. Hereinafter, the intra-picture coding maybe referred to as intra coding.

In the case of using the adaptive predictive coding method, due to adifference in correlation between pictures, a difference in predictionefficiency is caused. Consequently, a difference in compressionefficiency is caused. As a result, a situation occurs in which a codeamount varies in each picture. In addition, the variation occursregardless of a transmission band of a transmission path through which adata group (referred to as a bitstream) obtained by compression encodingis transmitted. Therefore, a general video encoding device and a generalvideo decoding device include a buffer memory for storing a bitstream soas to absorb a variation in the code amount and ensure transmission in apredetermined transmission band. The buffer memory is called a codedpicture buffer (CPB) in the AVC standard. The capacity of the buffermemory is greatly different depending on characteristics of a system towhich an encoding device and a decoding device are applied, but acapacity corresponding to 0.5 second multiplied by a transmission bitrate is typically provided, for example.

In various cases including channel switching of television broadcasts orspecial replay of storage type contents, it is required to startdecoding in the middle of a bitstream, i.e. random access, at the timeof recoding and transmitting a video. When decoding is started in themiddle of a bitstream generated by the inter-picture predictive coding,a video cannot be normally decoded because of the inter-pictureprediction process based on a non-decoded reference picture. Therefore,a general video encoding device implementing the adaptive predictivecoding performs encoding control (referred to as refresh) forappropriately inserting intra coding so as to obtain a normal decodedvideo within a predetermined period of time even when decoding isstarted in the middle of a bitstream.

One of refresh methods is instantaneous refresh for inserting a picture(referred to as an intra-coded picture) where the whole picture isencoded by intra-picture coding. FIG. 14 illustrates an example ofoperation of instantaneous refresh. In the drawing, an area indicated bya dashed border is a group of pictures which is a unit of refreshcontrol, and the group is called a refreshing group of pictures (RGOP).In the operation example illustrated in FIG. 14, the video encodingdevice inserts an intra-coded picture every four pictures, and controlssuch that three pictures subsequent to the intra-coded picture do notuse a picture encoded prior to the immediately preceding intra-codedpicture as a reference picture, that is, the inter-picture prediction isperformed within the refreshing group of pictures. In this manner, evenwhen starting decoding in the middle of a bitstream, the decoding devicecan obtain a correct decoded image by starting a decoding process from aleading intra-picture of each refreshing group of pictures. In the AVCdescribed in the above Non Patent Literature 1, an intra-coded picturewhich limits subsequent pictures such that subsequent pictures do notrefer to a picture encoded prior thereto, is called instantaneousdecoding refresh (IDR) picture and a special picture identifier isassigned to the IDR picture in a bitstream. A video encoding devicecompliant with the AVC standard can correctly notify a video decodingdevice of the correct timing to start decoding for refresh by encoding aleading picture of the refreshing group of pictures as an IDR picture.

However, it is a problem that the instantaneous refresh increasestransmission delay. As described above, generally, there is a highcorrelation in a video, in particular, temporally. Therefore, anintra-coded picture that cannot adopt inter-picture prediction requiresa larger code amount than other pictures in order to maintainpredetermined image quality. A larger difference in generated codeamount between pictures increases required capacity of a buffer memorywhich is provided for the video encoding device and the video decodingdevice. The increase of capacity of the buffer memory causes an increasein transmission delay between the encoding device and the decodingdevice. Therefore, the instantaneous refresh is not appropriate for ause requiring high real-time property, such as equipment remote controlthrough a video.

On the other hand, as a refresh method satisfying demands for a decreasein transmission delay, there is a method (referred to as gradualrefresh) for gradually refreshing an screen by the partial area(referred to as segment) which is obtained by dividing the screen, andperforming refresh across a plurality of pictures until refresh iscompleted. One of typical gradual refresh is intra-slice refresh, whichis disclosed in, for example, Patent Literature 1. A slice is a set ofcoding unit blocks in a picture and refers to a segment that isindependent of other coding unit blocks in the picture. An intra slicerefers to a slice where intra-frame coding is selected for all codingunits in the slice, and prediction using pixels in other slicesincluding another slice of the same frame, is not performed. Anintra-slice refresh performs such refresh in which a part of a slice ina picture is encoded as an intra slice and controls such that an areaencoded as an intra slice in each of consecutive pictures is moved sothat any area in the pictures is encoded as an intra slice at least oncewithin predetermined time period.

FIG. 15 illustrates an example of operation of intra-slice refresh. Apicture at the time t is indicated by P(t) below. In FIG. 15,P(t_(i-4)), P(t_(i)), and P(t_(i+4)) are start frames of gradual refreshand the four pictures are refreshed until refresh is completed. A period(in FIG. 15, corresponding to 4 pictures) from the start of refresh andto the end thereof is called a refreshing period. In FIG. 15, partialareas indicated by black paint show intra slices. During a refreshingperiod, refresh of an image is performed by setting each of all areas ina screen to an intra slice at least once.

In the intra-slice refresh illustrated in FIG. 15, in order to refreshcertainly, limitation is applied to a referable range for predictionalso outside the intra slice, in the same way as the instantaneousrefresh illustrated in FIG. 15. In FIG. 15, an area indicated by adashed border constitutes a group of partial areas, which is a unit forrefresh control, and is referred to as a refreshing group of segments(RGOS). Like the refreshing group of pictures in the instantaneousrefresh, each refreshing group of segments is limited not to refer to adifferent refreshing group of segments which starts from a picture priorto a first picture having an area belonging to the refreshing group ofsegments. A video decoding device which receives and decodes a bitstreamencoded as described above can obtain a correct decoded image ofpictures after the end position of the refreshing period withoutdisturbance in a whole screen by starting decoding from a leadingpicture within a refreshing period. Hereinafter, a leading picturewithin a refreshing period is referred to as a synchronization startingpicture. A first picture, from which a correct decoded image can beobtained without disturbance in a whole screen when encoding isperformed from the synchronization starting picture, is referred to as asynchronization completed picture.

Incidentally, the gradual refresh does not necessarily need to use anintra slice and is generally realized by limiting a prediction referencerelationship between refreshing groups of segments. FIG. 16 illustratesan example of a general gradual refresh. In order to refresh certainly,areas belonging to each refreshing group of segments indicated by adashed border are limited not to refer to a different refreshing groupof segments starting from a picture prior to a leading picture of therefreshing group of segments. Further, more generally, when it isensured that a decoded image after completion of refresh is sufficientlysimilar to an image decoded from the beginning of a bitstream, an areabelonging to each refreshing group of segments may refer to anotherrefreshing group of segments starting from a frame prior to a leadingframe of the refreshing group of segments.

In gradual refresh, an increase in a code amount due to refresh isdistributed to a whole refreshing period. That is, unlike an intra-codedpicture of the instantaneous refresh, there is no picture which causesan increase in a code amount in the whole screen. Therefore, a variationin a code amount between pictures is more reduced than that in the caseof using the instantaneous refresh. As a result, the required capacityof the buffer memory decreases and, furthermore, transmission delaybetween the encoding device and the decoding device is reduced.

On the other hand, in the case of using the gradual refresh, there is noan explicit refresh start point unlike an IDR picture. Therefore, avideo encoding device, which generates a bitstream by using gradualrefresh, multiplexes information on a synchronization starting pictureand a synchronization completed picture (refresh information) on abitstream and transfers the bitstream to a decoding device so that adecoding device can start decoding from the synchronization startingpicture and also restart image display from the synchronizationcompleted picture.

In the AVC described in Non Patent Literature 1, as a means where anencoding device transfers refresh information to a decoding device, adata group called a recovery point supplemental enhancement informationmessage (recovery point SEI message) is defined. An AVC-compliantencoding device transfers the recovery point SEI message to the decodingdevice by multiplexing the message on the bitstream. An AVC-compliantdecoding device can start decoding from the synchronization startingpicture and restart image display from the synchronization completedpicture according to the recovery point SEI message. The recovery pointSEI message includes information on the synchronization starting pictureand the synchronization completed picture and corresponds with both ofthe instantaneous refresh and the gradual refresh.

A list on FIG. 17 shows syntax elements configuring the recovery pointSEI message which is used to transfer refresh information from anAVC-compliant encoding device to an AVC-compliant decoding device.

recovery_frame_cnt is a parameter for notifying of a synchronizationcompleted picture. That is, for example, P(t_(i-4)), P(t_(i)), andP(t_(i+4)) illustrated in FIG. 14, and, for example, P(t_(i-1)),P(t_(i+3)), and P(t_(i+7)) illustrated in FIG. 15 are notified. A videodecoding device is notified of the paired synchronization startingpicture by existence of the recovery point SEI message itself. That is,an AVC-compliant video decoding device starts decoding from thesynchronization starting picture to which the recovery point SEI messageis associated and continues decoding until the synchronization completedpicture indicated by recovery_frame_cnt, thereby obtaining a decodedimage without disturbance in the whole screen. Therefore, the videodecoding device can select and display only images without disturbancein regard to a bitstream generated using the gradual refresh.

exact_match_flag is a parameter for notifying of whether a decoded imagein the case of starting decoding from the synchronization startingpicture is exactly matched with a decoded image in the case of receivingand decoding the bitstream from the beginning thereof, in thesynchronization completed picture indicated by recovery_frame_cnt.

broken_link_flag is a parameter for notifying of whether there is apossibility that disturbance will occur to the visibly unacceptableextent in a group of pictures existing until the synchronizationcompleted picture indicated by recovery_frame_cnt, when decoding isstarted from the synchronization starting picture.

changing_slice_group_idc is a parameter for notifying of whether thereis a partial area that does not affect completion of refresh even if adecoding process is omitted, in a group of pictures existing until thesynchronization completed picture indicated by recovery_frame_cnt, whendecoding is started from the synchronization starting picture.

The description related to an example of multiplexing of conventionalrefresh information with reference to the list of FIG. 17 is ended.

CITATION LIST Patent Literature

-   PLT 1: JP 2007-221411 A (paragraph 0005 and 0006)

Non Patent Literature

-   NPL 1: ISO/IEC 14496-10 Information technology-coding of    audio-visual objects Part 10: Advanced Video Coding, Dec. 15, 2010

SUMMARY OF INVENTION Technical Problem

When gradual refresh is used, refresh of a screen is partially completedin pictures between a synchronization starting picture and asynchronization completed picture. When important information that needsto be instantaneously notified to a viewer exists in partial areas whererefresh is completed, it is preferred to start partially displayingareas where refresh is completed, instead of waiting for thesynchronization completed picture. However, there is no means forallowing a video decoding device to easily know portions in a screenwhere refresh is completed, when such a method is used that thesynchronization starting picture and the synchronization completedpicture are notified of by the recovery point SEI message. Therefore,there is a problem that the video decoding device cannot perform displayuntil the synchronization completed picture, that is, delay of displayoccurs.

On the other hand, when a reference area restriction for each refreshinggroup of segments is strictly kept, the video decoding device may know arange which is referred to in a prediction process for each of partialimages which are prediction units, during decoding. Therefore, the videodecoding device can obtain refreshed partial areas by calculation.However, in case the video decoding device obtains refreshed partialareas through calculation using prediction reference range information,this causes a problem that a computation amount of the video decodingdevice increases.

When the reference area restriction for each refreshing group ofsegments is not strictly kept, that is, when exact_match_flag of therecovery point SEI message is set to 0, a decoder cannot know refreshedpartial areas even through calculation using the prediction referencerange information. Therefore, in order for the decoder to know refreshedpartial areas through calculation using the prediction reference rangeinformation, a prediction reference range needs to be limited in thevideo encoding device. That is, in case the video decoding deviceobtains refreshed partial areas through calculation using the predictionreference range information, such problem occurs that video compressionefficiency is reduced, thereby relatively reducing video quality in asystem in which exact matching of a decoded image is not necessarilyrequired.

The present invention has been thus made in view of such problems, andits object is to provide a video encoding device, a video encodingmethod, and a program, capable of notifying a decoding device of apartial area in a screen which can start being displayed until asynchronization completed picture without increasing a computationamount of a decoding device in gradual refresh.

Another object of the present invention is to provide a video encodingdevice, a video encoding method, and a program, capable of notifying adecoding device of a partial area in a screen which can start beingdisplayed until a synchronization completed picture without reducingvideo quality in gradual refresh.

Another object of the present invention is to provide a video decodingdevice, a video decoding method, and a program, capable of, when abitstream generated by using gradual refresh is decoded and a video isreplayed, starting displaying partially until a synchronizationcompleted picture without increasing a computation amount.

Another object of the present invention is to provide a video decodingdevice, a video decoding method, and a program, capable of, when abitstream generated by using gradual refresh is decoded and a video isreplayed, starting displaying a high-quality video partially until asynchronization completed picture.

Solution to Problem

A video decoding device according to the present invention includes: ademultiplexer which demultiplexes a video bitstream including video dataof an encoded slice, Supplemental-Enhancement-Information having firstinformation indicating a leading picture in gradual refresh, andSupplemental-Enhancement-Information having second informationindicating segments where a refresh has completed in a current picture;an extractor which extracts the second information from a message whichis part of the demultiplexed Supplemental-Enhancement-Information; and avideo decoder which decodes image data from the demultiplexed videobitstream by using at least inter prediction, wherein the video decoderstarts decoding based on the leading picture in gradual refresh.

A video decoding method according to the present invention includes:demultiplexing a video bitstream including video data of an encodedslice, Supplemental-Enhancement-Information having first informationindicating a leading picture in gradual refresh, andSupplemental-Enhancement-Information having second informationindicating segments where a refresh has completed in a current picture;extracting the second information from a message which is part of thedemultiplexed Supplemental-Enhancement-Information; and decoding imagedata from the demultiplexed video bitstream by using at least interprediction, wherein the decoding is started based on the leading picturein gradual refresh.

A non-transitory computer readable information recording medium storinga video decoding program, when executed by a processor, performs:demultiplexing a video bitstream including video data of an encodedslice, Supplemental-Enhancement-Information having first informationindicating a leading picture in gradual refresh, andSupplemental-Enhancement-Information having second informationindicating segments where a refresh has completed in a current picture;extracting the second information from a message which is part of thedemultiplexed Supplemental-Enhancement-Information; and decoding imagedata from the demultiplexed video bitstream by using at least interprediction, wherein the video decoding is started based on the leadingpicture in gradual refresh.

Advantageous Effects of Invention

According to the present invention, when a video decoding devicereceives and replays a bitstream generated by a video encoding device inthe middle thereof, partial display can be started until asynchronization completed picture, thereby reducing display delay.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 It depicts a block diagram illustrating a configuration exampleof a video encoding device of a first exemplary embodiment according tothe present invention.

FIG. 2 It depicts a flowchart illustrating an operation example of thevideo encoding device of the first exemplary embodiment.

FIG. 3 It depicts an explanatory diagram illustrating an example ofvideo encoding by gradual refresh.

FIG. 4 It depicts an explanatory diagram illustrating an example ofmultiplexing display-enabled area information.

FIG. 5 It depicts an explanatory diagram illustrating another example ofmultiplexing display-enabled area information.

FIG. 6 It depicts an explanatory diagram illustrating another example ofmultiplexing display-enabled area information.

FIG. 7 It depicts an explanatory diagram illustrating another example ofmultiplexing display-enabled area information.

FIG. 8 It depicts a block diagram illustrating a configuration exampleof a video decoding device of a second exemplary embodiment according tothe present invention.

FIG. 9 It depicts a flowchart illustrating an operation example of thevideo decoding device of the second exemplary embodiment.

FIG. 10 It depicts a block diagram illustrating a configuration exampleof a video encoding device of a third exemplary embodiment according tothe present invention.

FIG. 11 It depicts a block diagram illustrating a configuration exampleof a video encoding device of a fourth exemplary embodiment according tothe present invention.

FIG. 12 It depicts a flowchart illustrating an operation example of thevideo encoding device of the fourth exemplary embodiment.

FIG. 13 It depicts a block diagram illustrating an example of aninformation processing system using a program according to the presentinvention.

FIG. 14 It depicts an explanatory diagram illustrating an operationexample of instantaneous refresh.

FIG. 15 It depicts an explanatory diagram illustrating an operationexample of intra-slice refresh.

FIG. 16 It depicts an explanatory diagram illustrating an example ofgeneralized gradual refresh.

FIG. 17 It depicts an explanatory diagram illustrating examples ofsyntax elements constituting recovery point supplemental enhancementinformation message.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of the present invention will be described belowwith reference to accompanying drawings.

First Exemplary Embodiment

FIG. 1 is a block diagram of a video encoding device according to afirst exemplary embodiment of the present invention. As illustrated inthe drawing, the video encoding device of the first exemplary embodimentincludes a video encoder 101, a refresh controller 102, adisplay-enabled area encoder 103, and a multiplexer 104. The presentexemplary embodiment is characterized in that the display-enabled areaencoder 103 which encodes display-enabled area information of eachpicture obtained from the refresh controller 102 for supplying to themultiplexer 104.

The video encoder 101 performs encoding on each of pictures in an inputvideo and supplies a bitstream of the video to the multiplexer 104.

When an adaptive predictive coding is performed in the video encoder101, the refresh controller 102 supplies a control signal to the videoencoder 101 such that prediction restriction is kept between refreshinggroups of segments so as to perform intended refresh. The refreshcontroller 102 supplies display-enabled area information of each pictureobtained from the refreshing groups of segments to the display-enabledarea encoder 103.

The display-enabled area encoder 103 encodes the display-enabled areainformation supplied from the refresh controller 102 and supplies theencoded display-enabled area information to the multiplexer 104 as adisplay-enabled area information bitstream.

The multiplexer 104 multiplexes a video bitstream obtained from thevideo encoder 101 and the display-enabled area information bitstreamobtained from the display-enabled area encoder 103 and outputs themultiplexed bitstream as a bitstream.

A video encoding process by the video encoding device of the firstexemplary embodiment will be described below with reference to aflowchart of FIG. 2.

In step S10001, the refresh controller 102 supplies control informationdefining a refresh operation to the video encoder 101 and thedisplay-enabled area encoder 103.

In step S10002, the video encoder 101 encodes respective pictures of aninput video and supplies a video bitstream thereof to the multiplexer104.

In step S10003, when a picture to be currently encoded is a picturebetween a synchronization starting picture and a synchronizationcompleted picture, the process proceeds to step S10004. When the pictureto be currently encoded is not a picture between the synchronizationstarting picture and the synchronization completed picture, processingof step S10004 is skipped and the process proceeds to step S10005.

In step S10004, the display-enabled area encoder 103 encodes informationdefining a display-enabled area of each picture and outputs a bitstreamthereof to the multiplexer 104.

In step S10005, the multiplexer 104 multiplexes a video bitstreamsupplied from the video encoder 101 and a display-enabled areainformation bitstream supplied from the display-enabled area encoder 103and outputs a bitstream.

In step S10006, when the bitstream output in step S10005 corresponds toa final picture to be encoded, video encoding is completed. In a casewhere the bitstream does not correspond to the final picture, theprocess returns to S10001.

According to the above configuration, in a case in which the videoencoding device generates a bitstream by using gradual refresh, thevideo encoding device can generate a bitstream so that a video decodingdevice can start partial display until the synchronization completedpicture and reduce display delay, when the video decoding devicereceives and replays the bitstream in the middle of the bitstream. Thisis because the video decoding device can know an area that can bedisplayed partially in pictures until the synchronization completedpicture since the multiplexer 104 receives control information defininga display-enabled start area in each picture from the display-enabledarea encoder 103, multiplexes the control information on a bitstream,and transmits the control information to the video decoding device.

EXAMPLE

A specific example of the video encoding device of the above firstexemplary embodiment will be described below.

In the present example, with respect to a progressive video in which aspatial resolution for each frame is 320×240 pixels, the most left areaof 64×240-pixel areas obtained by uniformly dividing a picture by 5 in ahorizontal direction is set as an intra-coded segment, and refresh isperformed so that an intra-coded segment is shifted so as not to beoverlapped with each other through 5 pictures.

FIG. 3 illustrates a specific case where refresh is performed. In FIG.3, a picture P(t_(i)) at time t_(i) is assumed as a synchronizationstarting picture, and P(t_(i+4)) is assumed as a synchronizationcompleted picture. A refresh completion segment in the picture P(t) attime t indicates an area set as an intra-coded segment one time fromtime t_(i) to time t. In this case, respective display-enabled areas ofpictures P (t_(i)), P(t_(i+1)), P(t_(i+2)), P(t_(i+3)) and P(t_(i+4))are 64×240-pixel, 128×240-pixel, 192×240-pixel, 256×240-pixel, and320×240-pixel rectangular areas from the left of the pictures,respectively. The display-enabled area encoder 103 encodes therespective display-enabled areas for supplying to the multiplexer 104.

Information of the above-described display-enabled areas may bemultiplexed on a bitstream as a part (referred to as a partialdisplay-enabled area supplemental enhancement information message) of asupplemental enhancement information message, according to thedescription of “Specification of syntax functions, categories, anddescriptors” of Non Patent Literature 1, for example.

An example of multiplexing of display-enabled area information in a listof FIG. 4 will be described below.

Assuming that a picture number of a picture to which the partialdisplay-enabled area supplemental enhancement information message isassociated is CurrPicOrderCnt in a case where decoding is started with apicture, which is assumed as a synchronization starting picture, definedby a picture number RecvStartPicOrderCnt obtained by Formula 1 below,recovery_starting_poc_cnt indicates that a display-enabled arearepresented in the partial display-enabled area supplemental enhancementinformation message is applied.

RecvStartPicOrderCnt=CurrPicOrderCnt−recovery_starting_poc_cnt  (Formula1)

partial_recovery_cnt_minus1 represents a number of rectangular areaswhich exist in the partial display-enabled area supplemental enhancementinformation message. A display-enabled area in a picture to which thepartial display-enabled area supplemental enhancement informationmessage is associated is obtained as a union of the display-enabledrectangular areas.

exact_match_flag[i] indicates whether a decoded image in a case wheredecoding is started from a picture defined by RecvStartPicOrderCnt isexactly matched with a decoded image in a case where a bitstream isreceived and decoded from the beginning thereof in the display-enabledrectangular area. In a case where a decoded value of exact_match_flag[i]is 1, it is indicated that exact matching of a decoded image is achievedwith respect to all pixels in the display-enabled rectangular area. In acase where a decoded value of exact_match_flag[i] is 0, it is indicatedthat there is a possibility that exact matching of a decoded image willnot be achieved with respect to all pixels in the display-enabledrectangular area.

recovery_rect_left_offset[i], recovery_rect_right_offset[i],recovery_rect_top_offset[i], and recovery_rect_bottom_offset[i] are agroup of parameters that designate a position on a screen of thedisplay-enabled rectangular area. Assuming that both a horizontalcoordinate and a vertical coordinate of an upper left pixel of a decodedimage are set to 0, and a horizontal coordinate and a verticalcoordinate of a lower right pixel of the decoded image are set toPicWidthInSamples−1 and PicHeightInSamples−1, respectively, when anupper left pixel horizontal coordinate, an upper left pixel verticalcoordinate, a lower right pixel horizontal coordinate, and a lower rightpixel vertical coordinate of the rectangular area in the picture definedin CurrPicOrderCnt are CurrRecvRectLeft[i], CurrRecvRectRight[i],CurrRecvRectTop[i], and CurrRecvRectBottom[i], values ofCurrRecvRectLeft[i], CurrRecvRectRight[i], CurrRecvRectTop[i], andCurrRecvRectBottom[i] are calculated by Formula 2 below.

CurrRecvRectLeft[i]=recovery_rect_left_offset[i]CurrRecvRectRight[i]=PicWidthInSamples−1−recovery_rect_right_offset[i]CurrRecvRectTop[i]=recovery_rect_top_offset[i]CurrRecvRectBottom[i]=PicHeightInSamples−1−recovery_rect_bottom_offset[i]  (Formula2)

Now, the description of the multiplexing example of the display-enabledarea information of FIG. 4 is ended.

The present example is an example in which display-enabled areainformation is directly encoded and is multiplexed on a bitstream as asupplemental enhancement information message, with respect to picturesfrom the synchronization starting picture to the synchronizationcompleted picture on a picture-by-picture basis. However, according tothe present invention, for example, with respect to a first picture, thedisplay-enabled area information is multiplexed as partialdisplay-enabled area supplemental enhancement information message shownin FIG. 4, and, with respect to subsequent pictures, update informationof the display-enabled area may be multiplexed on a bitstream on apicture-by-picture basis as the partial display-enabled area updatesupplemental enhancement information message shown in FIG. 5.

A multiplexing example of the display-enabled area information in a listof FIG. 5 will be described below.

partial_recovery_ref_poc_cnt indicates that, assuming that the picturenumber of a picture to which the partial display-enabled area updatesupplemental enhancement information message is associated isCurrPicOrderCnt, a display-enabled area of the picture is calculatedwith reference to another display-enabled area defined by the partialdisplay-enabled area supplemental enhancement information message, orthe partial display-enabled area update supplemental enhancementinformation message, associated with a picture defined by a picturenumber PartRecvRefPicOrderCnt calculated by Formula 3 below.

PartRecvRefPicOrderCnt=CurrPicOrderCnt−partial_recovery_ref_poc_cnt  (Formula3)

exact_match_flag[i] indicates whether a decoded image in a case wheredecoding is started from a picture defined byRecoveryStartingPicOrderCnt is exactly matched with a decoded image in acase where a bitstream is received and decoded from the beginningthereof in the display-enabled rectangular area. In a case where adecoded value of exact_match_flag[i] is 1, it is indicated that exactmatching of a decoded image is achieved with respect to all pixels in adisplay-enabled rectangular area. In a case where a decoded value ofexact_match_flag[i] is 0, it is indicated that there is a possibilitythat exact matching of a decoded image will not be achieved with respectto all pixels in a display-enabled rectangular area.

recovery_rect_left_offset_decr[i], recovery_rect_right_offset_decr[i],recovery_rect_top_offset_decr[i], andrecovery_rect_bottom_offset_decr[i] are a group of parameters forupdating a position on a screen of the display-enabled rectangular areain the picture. Assuming that an upper-left pixel-horizontal coordinate,an upper-left pixel-vertical coordinate, a lower-right pixel-horizontalcoordinate, and a lower-right pixel-vertical coordinate in an i-thdisplay-enabled rectangular area, determined in a picture defined byPartRecvRefPicOrderCnt, are RefRecvRectLeft[i], RefRecvRectRight[i],RefRecvRectTop[i], and RefRecvRectBottom[i], values of the upper-leftpixel-horizontal coordinate CurrRecvRectLeft[i], the upper-leftpixel-vertical coordinate CurrRecvRectRight[i], the lower-rightpixel-horizontal coordinate CurrRecvRectTop[i], and the lower-rightpixel-vertical coordinate CurrRecvRectBottom[i] in the rectangular areain the picture defined in CurrPicOrderCnt are calculated by Formula 4below.

CurrRecvRectLeft[i]=RefRecvRectLeft[i]-recovery_rect_left_offset_decr[i]CurrRecvRectRight[i]=RefRecvRectRight[i]+recovery_rect_right_offset_decr[i]CurrRecvRectTop[i]=RefRecvRectTop[i]-recovery_rect_top_offset_decr[i]CurrRecvRectBottom[i]=RefRecvRectBottom[i]+recovery_rect_bottom_offset_decr[i]  (Formula4)

With respect to recovery_rect_left_offset_decr[i],recovery_rect_right_offset_decr[i], recovery_rect_top_offset_decr[i],and recovery_rect_bottom_offset_decr[i], when each variable does notexist on the bitstream, its value is considered to be 0.

Now, the description of the multiplexing example of the display-enabledarea update information of FIG. 5 is ended.

Further, the present example is an example in which display-enabled areainformation is multiplexed on a bitstream as a supplemental enhancementinformation message independent of other supplemental enhancementinformation messages in FIGS. 4 and 5. However, according to the presentinvention, for example, in the synchronization starting picture,information of partial display-enabled area as illustrated in the listof FIG. 6 may be superposed on the recovery point supplementalenhancement information message illustrated in the list of FIG. 17, andmay be multiplexed on a bitstream.

A multiplexing example of the display-enabled area informationillustrated in the list of FIG. 6 will be described below.

partital_recovery_info_present_flag is a parameter indicating whetherinformation of the partial display-enabled area exists in a relevantsupplemental enhancement information message.

Since other parameters displayed in the list of FIG. 6 are identical tothe parameters displayed in the list of FIG. 4 and FIG. 17, adescription thereof is omitted herein.

Now, the description of the multiplexing example of the display-enabledarea information of FIG. 6 is ended.

Further, in the above description of the video encoding process in thevideo encoding device of the first exemplary embodiment of the presentinvention, an operation example of encoding the display-enabled areainformation and multiplexing the display-enabled area information on abitstream, for each picture having a display-enabled area, isillustrated. However, according to the present invention, thedisplay-enabled area information in the synchronization starting picturemay be superposed on the recovery point supplemental enhancementinformation message and may be multiplexed on a bitstream until thesynchronization completed picture as illustrated in the list of FIG. 7,or the display-enabled area information may be encoded and multiplexedon a bitstream for every several pictures.

A multiplexing example of the display-enabled area information that isillustrated in FIG. 7 will be described below.

partial_recovery_update_info_present_flag[i] is a parameter indicatingwhether update information of an i-th display-enabled area exists in apicture after the synchronization starting picture.

Since other parameters illustrated in the list of FIG. 7 are identicalto parameters displayed in the list of FIG. 6 and FIG. 17, a descriptionthereof is omitted herein.

Now, the description of the multiplexing example of the display-enabledarea information of FIG. 7 is ended.

The present example is an example in which the display-enabled areainformation is multiplexed as a supplemental enhancement informationmessage with respect to each picture. However, according to the presentinvention, the display-enabled area information may be multiplexed with,for example, a sequence parameter set used for encoding and decoding ofa whole bitstream or the display-enabled area information may bemultiplexed with, for example, a picture parameter set.

In addition, in the present example, the display-enabled areainformation is encoded with respect to all pictures from thesynchronization starting picture to the synchronization completedpicture and is multiplexed on the bitstream. However, the presentinvention is not limited to encoding of the display-enabled areainformation for all pictures from the synchronization starting pictureto the synchronization completed picture, and the display-enabled areainformation may be encoded selectively for certain pictures from thesynchronization starting picture to the synchronization completedpicture and may be multiplexed on a bitstream.

In the present example, refresh is performed by shifting an intra-codedsegment from the left to the right in a screen at uniform intervalswithout overlapping. However, the present invention is not limited tothe above refresh, and a refresh direction may be arbitrarily selected.For example, refresh may be performed in an arbitrary direction, such asfrom right to left, up to down, upper left to lower right, from thecenter of a picture to left and right, or along an eddy shape from thecenter of a picture. In addition, the method of shifting an intra-codedsegment for refresh is arbitrary. A size of the intra-coded segment mayvary with respect to respective pictures and the same area may be set asthe intra-coded segment two or more times during a refreshing period. Inaddition, as known from the description of gradual refresh describedherein, the present invention is not limited to refresh based onintra-coded segments, and refresh may be performed using an arbitrarymethod, such as a method of limiting a prediction range of inter-picturepredictive coding.

Although the display-enabled area is encoded as offset values from theupper, lower, left and right edges of a picture and is multiplexed on abitstream in the present example, the present invention is not limitedto the configuration in which the display-enabled area is encoded asoffset values from the upper, lower, left and right edges of a picture,and the display-enabled area may be encoded by using an arbitraryexpression method.

Although the display-enabled area information is multiplexed accordingto the describing method of the AVC described in Non Patent Literature1, the present invention is not limited to use of the AVC, and may beapplicable to other video encoding methods or to an arbitrarydimensional video encoding method instead of the two dimensional video.

In the present example, although the display-enabled area is encoded asa set of rectangular areas on a two dimensional image and is multiplexedon a bitstream, the present invention is not limited to the encoding ofthe display-enabled area as the set of rectangular areas on thetwo-dimensional image, and the display-enabled area may be encoded byusing an arbitrary expression method instead of the set of rectangularareas or may be encoded as an arbitrary dimensional area.

The description of the video encoding device of the first exemplaryembodiment of the present invention is ended now.

Second Exemplary Embodiment

FIG. 8 is a block diagram of a video decoding device according to asecond exemplary embodiment of the present invention. As illustrated inFIG. 8, the video decoding device of the second exemplary embodimentincludes a demultiplexer 201, a video decoder 202, a display-enabledarea decoder 203, and a video output controller 204. The presentexemplary embodiment is characterized in that the display-enabled areadecoder 203 that decodes and outputs information of a display-enabledarea in each picture is provided, and the video output controller 204that interprets the display-enabled area and performs control such thata decoded image other than the display-enabled area is not output isalso provided.

The demultiplexer 201 demultiplexes a bitstream, extracts a videobitstream and a display-enabled area information bitstream, and suppliesthe video bitstream to the video decoder 202, and supplies thedisplay-enabled area information bitstream to the display-enabled areadecoder 203.

The video decoder 202 decodes the video bitstream and supplies anobtained reconstructed image to the video output controller 204.

The display-enabled area decoder 203 decodes the display-enabled areainformation bitstream and supplies obtained display-enabled areainformation to the video output controller 204.

The video output controller 204 controls such that an image outside thedisplay-enabled area obtained from the display-enabled area decoder 203is not displayed with respect to the reconstructed image supplied fromthe video decoder 202, and outputs a processing result as a decodedvideo.

A video decoding process by the video decoding device of the secondexemplary embodiment will be described below with reference to aflowchart of FIG. 9.

In step S20001, the demultiplexer 201 demultiplexes a bitstream,extracts a video bitstream and a display-enabled area informationbitstream, and supplies the video bitstream to the video decoder 202,and the display-enabled area information bitstream to thedisplay-enabled area decoder 203.

In step S20002, the video decoder 202 decodes the video bitstream andsupplies an obtained reconstructed image to the video output controller204.

In step S20003, when display-enabled area information is associated witha picture, the process proceeds to step S20004. When display-enabledarea information is not associated with the picture, processing of stepS20004 is skipped and the process proceeds to step S20005.

In step S20004, the display-enabled area decoder 203 decodes thedisplay-enabled area information bitstream and supplies obtaineddisplay-enabled area information to the video output controller 204.

In step S20005, the video output controller 204 controls such that animage outside the display-enabled area obtained from the display-enabledarea decoder 203 is not displayed with respect to the reconstructedimage supplied from the video decoder 202, and outputs a processingresult as a decoded video.

In step S20006, when the bitstream decoded in step S20002 corresponds toa final picture to be decoded, video decoding is ended. In a case wherethe bitstream does not correspond to the final picture, the processreturns to S20001.

According to the above configuration, when receiving and replaying abitstream generated by using gradual refresh in the middle thereof, thevideo decoding device starts display partially without obtaining adisplay-enabled area from a prediction reference range by calculation,rather than waits for decoding of a synchronization completed picture,thereby reducing display delay. This is because the video outputcontroller 204 can control such that an image outside thedisplay-enabled area is not output as a decoded video since the videothe decoding device receives information defining a display-enabled areaas a bitstream from the video encoding device, and the demultiplexer 201supplies the information to the display-enabled area decoder 203.

Now, the description of the video decoding device of the secondexemplary embodiment of the present invention is ended.

Third Exemplary Embodiment

FIG. 10 is a block diagram of a video encoding device according to athird exemplary embodiment of the present invention. As illustrated inFIG. 10, the video encoding device of the third exemplary embodiment issimilar in that the same components is included, but is different inthat a control signal is supplied to the display-enabled area encoder103, rather than the video encoder 101, as compared with the videoencoding device of the first exemplary embodiment illustrated in FIG. 1.Since operations of the refresh controller 102 and the multiplexer 104among the components of the video encoding device of the third exemplaryembodiment are identical to operations of those of the video encodingdevice of the first exemplary embodiment, a description will be givenfor remaining blocks below.

The video encoder 101 performs encoding on each of pictures constitutingan input video and provides a bitstream of the video to the multiplexer104. In addition, information related to an area in which refresh iscompleted is supplied to the display-enabled area encoder 103.

The display-enabled area encoder 103 calculates and encodesdisplay-enabled area information based on display-enabled areainformation supplied from the refresh controller 102 and refreshcompleted area information supplied from the video encoder 101, andsupplies the display-enabled area information to the multiplexer 104 asa display-enabled area information bitstream.

A video encoding process by the video encoding device of the thirdexemplary embodiment is represented by the flowchart of FIG. 2 like thevideo encoding process by the video encoding device of the firstexemplary embodiment. In this case, a description for a flow of thevideo encoding process by the video encoding device of the thirdexemplary embodiment will be omitted.

According to the above configuration, an effect is obtained in which adisplay-enabled area wider than that of the video encoding device of thefirst exemplary embodiment can be transferred to a video decodingdevice. This is because in a case where intra coding is eventuallyselected independently of a control signal supplied from the refreshcontroller 102 and thereby a display-enabled area is generated bycompleting refresh in the video encoder 101, the display-enabled areaencoder 103 can encode a wider display-enabled area and supply thedisplay-enabled area to the multiplexer 104.

Now, the description of the video encoding device of the third exemplaryembodiment of the present invention is ended.

Fourth Exemplary Embodiment

FIG. 11 is a block diagram of a video encoding device according to afourth exemplary embodiment of the present invention. As illustrated inFIG. 11, the video encoding device of the fourth exemplary embodiment isdifferent in that a display-enabled area encoding controller 105 isnewly included as a component thereof, as compared with the videoencoding device of the first exemplary embodiment illustrated in FIG. 1.Since operations of the video encoder 101, the refresh controller 102and the multiplexer 104 among the components of the video encodingdevice of the fourth exemplary embodiment are identical to operations ofthose of the video encoding device of the first exemplary embodiment, adescription will be given for remaining blocks below.

The display-enabled area encoding controller 105 supplies a controlsignal for controlling encoding of display-enabled area information tothe display-enabled area encoder 103.

The display-enabled area encoder 103 encodes information, of which theencoding is indicated by the control signal supplied from thedisplay-enabled area encoding controller 105, among display-enabled areainformation supplied from the refresh controller 102 and supplies theinformation to the multiplexer 104 as a display-enabled area informationbitstream.

A video encoding process by the video encoding device of the fourthexemplary embodiment will be described below with reference to aflowchart of FIG. 12.

In step S10001, the refresh controller 102 provides control informationdefining a refresh operation to the video encoder 101 and thedisplay-enabled area encoder 103.

In step S10002, the video encoder 101 encodes respective pictures of aninput video and provides a video bitstream thereof to the multiplexer104.

In step S10003, in a case where a picture to be currently encoded is apicture between a synchronization starting picture and a synchronizationcompleted picture, the process proceeds to step S10007. In the casewhere a picture to be currently encoded is not a picture from thesynchronization starting picture to the synchronization completedpicture, processing of step S10007 and step S10004 is skipped and theprocess proceeds to step S10005.

In step S10007, when a current display-enabled area is an area to beencoded, the process proceeds to step S10004. Otherwise, processing ofstep S10004 is skipped and the process proceeds to step S10005.

In step S10004, the display-enabled area encoder 103 encodes informationdefining a display-enabled area of each picture, and outputs a bitstreamthereof to the multiplexer 104.

In step S10005, the multiplexer 104 multiplexes a video bitstreamsupplied from the video encoder 101 and a display-enabled areainformation bitstream supplied from the display-enabled area encoder 103and outputs the multiplexed bitstream as a bitstream.

In step S10006, when the bitstream output in step S10005 corresponds toa final picture to be encoded, video encoding is ended. In a case wherethe bitstream does not correspond to the final picture, the processreturns to S10001.

According to the above configuration, such effect is obtained that areduction in compression efficiency of the video data can be relativelysuppressed when the video encoding device notifies the video decodingdevice of a partial area where display can be started before thesynchronization completed picture, in addition to the effect obtained bythe video encoding device of the first exemplary embodiment. This isbecause a data amount required to transfer the display-enabled areainformation can be reduced since the display-enabled area encodingcontroller 105 limits the display-enabled area to be encoded.

Now, the description of the video encoding device of the fourthexemplary embodiment of the present invention is ended.

As it is obvious from the description of the exemplary embodiments ofthe present invention, the present invention may be realized byhardware, or a computer program.

An information processing system illustrated in FIG. 13 includes aprocessor 1001, a program memory 1002, and storage mediums 1003 and1004. The storage medium 1003 and the storage medium 1004 may beseparate storage media, or storage areas included in the same storagemedium. As the storage medium, a magnetic storage medium such as a harddisk can be used as the storage medium.

In the information processing system illustrated in FIG. 13, the programmemory 1002 stores programs for implementing the functions of therespective blocks illustrated in FIG. 1, FIG. 8, FIG. 10, and FIG. 11.The processor 1001 performs processes according to the program stored inthe program memory 1002 to implement the functions of the video encodingdevice or the video decoding device illustrated in FIG. 1, FIG. 8, FIG.10, and FIG. 11.

Part or all of the aforementioned exemplary embodiments can be describedas Supplementary notes mentioned below, but the structure of the presentinvention is not limited to the following structures.

(Supplementary Note 1)

A video encoding device comprising: video encoding means for encodingimage data of an input moving image based on prediction and generating avideo bitstream of encoded pictures; refresh control means forrefreshing such that a partial area in the picture is assumed as a unitarea to be refreshed and the unit area to be refreshed is moved on apicture-by-picture basis; display-enabled area encoding means forencoding a display-enabled area for each picture in refreshing andgenerating a display-enabled area information bitstream; andmultiplexing means for multiplexing a video bitstream and thedisplay-enabled area information bitstream.

(Supplementary Note 2)

The video encoding device according to Supplementary note 1, wherein thedisplay-enabled area encoding means generates the display-enabled areainformation bitstream by using a difference between a display-enabledarea in a picture to be encoded and a display-enabled area in a pictureencoded in the past.

(Supplementary Note 3)

The video encoding device according to Supplementary note 1 or 2,further comprising display-enabled area encoding control means forcontrolling whether to encode the display-enabled area, wherein thedisplay-enabled area encoding means selects and encodes adisplay-enabled area which is determined to be encoded by thedisplay-enabled area encoding control means.

(Supplementary Note 4)

The video encoding device according to any one of Supplementary notes 1to 3, wherein the refresh control means performs refresh by intracoding.

(Supplementary Note 5)

The video encoding device according to any one of Supplementary notes 1to 4, wherein the refresh control means shifts a unit area to berefreshed within a prediction limitation range configured by a pluralityof pictures, and the video encoding means excludes a predicted value byintra-picture prediction or inter-picture prediction which is beyond theprediction limitation range when performing encoding based onprediction.

(Supplementary Note 6)

A video decoding device comprising: demultiplexing means fordemultiplexing a bitstream including video data and a bitstreamincluding display-enabled area information in an image to be decoded;video decoding means for decoding the demultiplexed video bitstreambased on prediction and generating image data; video output controlmeans for limiting an output area of the image data based on thedemultiplexed display-enabled area information; and display-enabled areadecoding means for decoding the demultiplexed display-enabled areainformation bitstream according to a predetermined method and extractingat least a part of the display-enabled area information.

(Supplementary Note 7)

The video decoding device according to Supplementary note 6, wherein thedisplay-enabled area information bitstream includes at least adifference between a display-enabled area in a picture to be decoded anda display-enabled area in a picture decoded in the past, and thedisplay-enabled area decoding means extracts the difference between thedisplay-enabled area in the picture to be decoded and thedisplay-enabled area in the picture decoded in the past from thedisplay-enabled area information bitstream and obtains a display-enabledarea in the picture to be decoded.

(Supplementary Note 8)

A video encoding method comprising: encoding image data of an inputmoving image based on prediction and generating a video bitstream ofencoded pictures; refreshing such that a partial area in the picture isassumed as a unit area to be refreshed and the unit area to be refreshedis moved on a picture-by-picture basis; encoding a display-enabled areafor each picture and generating a display-enabled area informationbitstream in refreshing; and multiplexing the video bitstream and thedisplay-enabled area information bitstream.

(Supplementary Note 9)

The video encoding method according to Supplementary note 8, furthercomprising generating the display-enabled area information bitstream byusing a difference between a display-enabled area in a picture to beencoded and a display-enabled area in a picture encoded in the past.

(Supplementary Note 10)

The video encoding method according to Supplementary note 8 or 9,further comprising controlling whether to encode the display-enabledarea, and selecting and encoding a display-enabled area which isdetermined to be encoded by the control.

(Supplementary Note 11)

The video encoding method according to any one of Supplementary notes 8to 10 further comprising refreshing by intra coding when picture refreshis performed.

(Supplementary Note 12)

The video encoding method according to any one of Supplementary notes 8to 11, wherein, when picture refresh is performed, shifting a unit areato be refreshed within a prediction limitation range configured by aplurality of pictures, and excluding a predicted value by intra-pictureprediction or inter-picture prediction which is out of the predictionlimitation range when performing encoding based on prediction.

(Supplementary Note 13)

A video decoding method comprising: demultiplexing a bitstream includingvideo data and a bitstream including display-enabled area information inan image to be decoded; decoding the demultiplexed video bitstream basedon prediction and generating image data; limiting an output area of theimage data based on the demultiplexed display-enabled area information;and decoding the demultiplexed display-enabled area informationbitstream according to a predetermined method and extracting at least apart of the display-enabled area information.

(Supplementary Note 14)

The video decoding device according to Supplementary note 13, furthercomprising extracting a difference between a display-enabled area in apicture to be decoded and a display-enabled area in a picture decoded inthe past from the display-enabled area information bitstream includingat least the difference between the display-enabled area in the pictureto be decoded and the display-enabled area in the picture decoded in thepast and obtaining a display-enabled area in the picture to be decoded.

(Supplementary Note 15)

A video encoding program which causes a computer to perform: a videoencoding process of encoding image data of an input moving image basedon prediction and generating a video bitstream of encoded pictures; arefresh control process of refreshing such that a partial area in thepicture is assumed as a unit area to be refreshed and the unit area tobe refreshed is moved on a picture-by-picture basis; a display-enabledarea encoding process of encoding a display-enabled area for eachpicture and generating a display-enabled area information bitstream inrefreshing; and a multiplexing process of multiplexing a video bitstreamand the display-enabled area information bitstream.

(Supplementary Note 16)

The video encoding program according to Supplementary note 15, whereinin the display-enabled area encoding process, the computer is caused toperform generating the display-enabled area information bitstream byusing a difference between a display-enabled area in a picture to beencoded and a display-enabled area in a picture encoded in the past.

(Supplementary Note 17)

The video encoding program according to Supplementary note 15 or 16,wherein the computer is caused to perform the display-enabled areaencoding control process of controlling whether to encode thedisplay-enabled area, and in the display-enabled area encoding process,to perform selecting and encoding a display-enabled area which isdetermined to be encoded in the display-enabled area encoding controlprocess.

(Supplementary Note 18)

The video encoding program according to any one of Supplementary note 15to 17, wherein in the refresh control process, the computer is caused toperform refresh by intra coding.

(Supplementary Note 19)

The video encoding program according to any one of Supplementary note 15to 18, wherein in the refresh control process, the computer is caused toperform shifting a unit area to be refreshed within a predictionlimitation range configured by a plurality of pictures, and in the videoencoding process, to perform excluding a predicted value byintra-picture prediction or inter-picture prediction which is out of theprediction limitation range when encoding is performed based onprediction.

(Supplementary Note 20)

A video decoding program which causes a computer to perform: ademultiplexing process of demultiplexing a bitstream including videodata and a bitstream including display-enabled area information in animage to be decoded; a video decoding process of decoding thedemultiplexed video bitstream based on prediction and generating imagedata; a video output control process of limiting an output area of theimage data based on the demultiplexed display-enabled area information;and a display-enabled area decoding process of decoding thedemultiplexed display-enabled area information bitstream according to apredetermined method and extracting at least a part of thedisplay-enabled area information.

(Supplementary Note 21)

The video decoding program according to Supplementary note 20, whereinin the display-enabled area decoding process, the computer is caused toperform extracting a difference between a display-enabled area in apicture to be decoded and a display-enabled area in a picture decoded inthe past from the display-enabled area information bitstream includingat least the difference between the display-enabled area in the pictureto be decoded in display-enabled area and the display-enabled area inthe picture decoded in the past, and obtaining a display-enabled area inthe picture to be decoded.

While the present invention has been described with reference to theexemplary embodiments and examples, the present invention is not limitedto the aforementioned exemplary embodiments and examples. Variouschanges understandable to those skilled in the art within the scope ofthe present invention can be made to the structures and details of thepresent invention.

This application claims priority based on Japanese Patent ApplicationNo. 2012-141924 filed on Jun. 25, 2012, the disclosures of which areincorporated herein in their entirety.

REFERENCE SIGNS LIST

-   101 Video encoder-   102 Refresh controller-   103 Display-enabled area encoder-   104 Multiplexer-   105 Display-enabled area encoding controller-   201 Demultiplexer-   202 Video decoder-   203 Display-enabled area decoder-   204 Video output controller

1. A video decoding device comprising: a demultiplexing unit whichdemultiplexes a video bitstream including video data of an encodedslice, first Supplemental-Enhancement-Information having informationindicating segments where a refresh has completed in a current picture,and second Supplemental-Enhancement-Information having informationindicating a synchronization starting picture and a synchronizationcompleted picture; an extracting unit which extracts the informationindicating segments where a refresh has completed in a current picturefrom a message which is part of the demultiplexedSupplemental-Enhancement-Information; and a video decoding unit whichdecodes image data from the demultiplexed video bitstream by using atleast inter prediction, wherein the synchronization starting picture isa leading picture within a refreshing period, and the synchronizationcompleted picture is the end position of the refreshing period.
 2. Avideo decoding method comprising: demultiplexing a video bitstreamincluding video data of an encoded slice, firstSupplemental-Enhancement-Information having information indicatingsegments where a refresh has completed in a current picture, and secondSupplemental-Enhancement-Information having information indicating asynchronization starting picture and a synchronization completedpicture; extracting the information indicating segments where a refreshhas completed in a current picture from a message which is part of thedemultiplexed Supplemental-Enhancement-Information; and decoding imagedata from the demultiplexed video bitstream by using at least interprediction, wherein the synchronization starting picture is a leadingpicture within a refreshing period, and the synchronization completedpicture is the end position of the refreshing period.
 3. Anon-transitory computer readable information recording medium storing avideo decoding program, when executed by a processor, performs:demultiplexing a video bitstream including video data of an encodedslice, first Supplemental-Enhancement-Information having informationindicating segments where a refresh has completed in a current picture,and second Supplemental-Enhancement-Information having informationindicating a synchronization starting picture and a synchronizationcompleted picture; extracting the information indicating segments wherea refresh has completed in a current picture from a message which ispart of the demultiplexed Supplemental-Enhancement-Information; anddecoding image data from the demultiplexed video bitstream by using atleast inter prediction, wherein the synchronization starting picture isa leading picture within a refreshing period, and the synchronizationcompleted picture is the end position of the refreshing period.